Identify capsule shaped transistor thing. gray cylinder, has 4 colored rings

Thread Starter

Euphi223

Joined May 1, 2019
14
Im at my last straw here. Im not experienced with this stuff at all. its too late to quit the job. Ive come here for help.
part in question is on a 36v elec bicycle's front (main) head-light.
it comes from 1/2 L.E.D headlight wires. I actually got the headlight going for a disappointing short time.
LED HL is composed of x9 small led's. all sit in a round circuit board similar in size to a beer bottle cap. HL is fine alone, VERY bright infact.
-Im not sure how to i.d this thing in the first place,
-unsure if its stuffed.

Capicitor thing.jpg

Im desperate for assistance.
Cheers
 

Audioguru

Joined Dec 20, 2007
11,251
It looks like a power resistor.
Its size determines how much heat it can withstand and its resistance value is in the code of its color bars.
 

Analog Ground

Joined Apr 24, 2019
234
Your electrical circuit is probably something like this pic. Your thing is a power resistor. It's purpose is to limit and set the electrical current through the LEDs. DO NOT CONNECT the LED string directly to the battery. You could burn them out. Perhaps you could post a sharper picture of the resistor and make sure it accurately shows the color of the bands. The bands are a "color code" which can tell us the "value" of the resistor. You will want to get one of the same value (or close). If you borrow a "DVM" or "multimeter" you can easily test if the resistor is OK. It looks good in the pic. Generally, if burned out, it would look burned. So, better pic and borrow a meter.
 

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Thread Starter

Euphi223

Joined May 1, 2019
14
Thanks very much to all who replied, especially 'analog ground'! Really appreciate your attention to my stupid-ass question. Im such an electrical novice! I really need to learn the basics. Youtube is proving helpful atm.

I got a replacement from Jaycar. They advised me on a 5Ω. Didn't look like the old one, came as a white box.

Thanks very much guys :)
 

Audioguru

Joined Dec 20, 2007
11,251
I actually got the headlight going for a disappointing short time.
Did you connect the headlight without the resistor and caused the headlight to burn out in a short time?

The circuit for the headlight is too simple using only a resistor to limit some of the current, so it was probably made as cheap as possible in the country that makes cheap stuff. For 9 LEDs to fit in a circle in a bottle cap then they must be small and therefore use fairly low current like 24mA.
A white LED uses about 3.6V so 9 in series use 32.4V. If the power supply is exactly 36V then the remaining voltage is 3.6V and if the current in the LEDs must be 24mA then the resistance must be 3.6V/24mA= 150 ohms.
If you use the 5 ohms resistor from Jaycar (Down Under?) then the current would be 3.6V/5 ohms= 720mA which is 30 times too high and cause the LEDs to burn out. If a 150 ohms resistor is used then if the power supply is 30V instead of 36V the LEDs would be dim. Also if the power supply becomes 40V then the LEDs would be very bright and maybe burn out. So a constant current source circuit should have been used instead of a simple resistor.
 

Thread Starter

Euphi223

Joined May 1, 2019
14


My camera is rubbish! i cant get clear sharp photos. Anyway...This resistor has been replaced with the new box shaped one. Still no joy!! I opened the switch housing, which is attached to the handle bars. There are 3 switches --> HL, Horn, Left & Right turn signals. Very tight access to do anything in there! like micro surgery. Visually everything looked good. No dust, corrosion, and every point was connected to its place.





Theres something wrong some place down the line. The HL isnt getting power. Im too inexperienced to tackle it. I think i need to get out my white flag.

Thanks again guys
 

sagor

Joined Mar 10, 2019
126
If the old resistor was 150 ohm (Black Green Brown is 150 ohms, with Gold band for tolerance rating), and you used a 5 ohm instead, you may have blown the HL yourself. From the pictures, it does not look burnt out, so that was probably not the cause of your failure in the first place. If the HL is good, and the resistor is good (measure it), then the failure is likely in the switching circuit to turn it on...
 

Thread Starter

Euphi223

Joined May 1, 2019
14
The HL is fine. for some reason, probably inexperience, i assumed the HL didnt work because of the original resistor. I was wrong, not surprisingly. There is something wrong elsewhere. Im giving up.
Cheers
 
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